Definition: A shaft in the engine on which are the lobes (cams) that operate the valves. The camshaft is driven by the crankshaft, via a belt, chain or gears, at one half the crankshaft speed. One or more camshafts regulate the opening and closing of the valves in all piston engines.

Related Resources:

How the Engine Works
A basic explanation of the internal parts of an engine, what they do and how they work.

Engine Testing With A Vacuum Gauge
Vacuum gauges have been a valuable tool to mechanics for years. Even with modern computer controlled engines a vacuum gauge is still a valuable tool for diagnosing engine and transmission problems.